CVN, a protein isolated from cyanobacteria, is known to have anti-viral activity. By interfering with the interaction of the viral envelope glycoprotein gp120 of human immunodeficiency viruses (HIV) with the surface of a cell, CVN can block the entry of HIV into the cell at nanomolar concentrations (Boyd et al., Animicrob. Agents Chemother. 41: 1521-1530(1997); Dey et al., J. Virol. 74: 4562-4569 (2000)). CVN:gp120 interactions are governed by high affinity binding of CVN to the D1 and D3 arms of oligomannose-8 and oligomannose-9, two oligosaccharides that are abundant on the surface of HIV (Bewley et al., J. Am. Chem. Soc. 123: 3892-3902 (2001)). This unprecedented specificity arises from the presence of two extensive carbohydrate binding pockets that are specific for the disaccharide oligomannose-α (1-2) oligomannose-α, i.e., the termini of the more accessible D1 and D3 arms of oligomannose-8 and oligomannose-9 (Bewley, Structure 9: 931-940 (2001)).
It is an object of the present invention to enhance the anti-viral activity of CVN. This and other objects and advantages of the present invention, as well as additional inventive features, will become apparent from the detailed description provided herein.